johnsnownw Posted August 25, 2010 Share Posted August 25, 2010 I was thinking about going up one jet size for the pilot and main. At this point it would be for running stock set up. Anyone think this will cause the bike to run too rich? As it stand now I have the mixtures turned out about 4.3 turns. I figure that if I get the new jets, I still have quite a bit of wriggle room with the mixture screws. Thanks Link to comment Share on other sites More sharing options...
Moderator Cynic Posted August 25, 2010 Moderator Share Posted August 25, 2010 I was thinking about going up one jet size for the pilot and main. At this point it would be for running stock set up. Anyone think this will cause the bike to run too rich? As it stand now I have the mixtures turned out about 4.3 turns. I figure that if I get the new jets, I still have quite a bit of wriggle room with the mixture screws. Thanks ? The mixture screws only control a small part of the process, if you are at altitude then maybe lean her off with a smaller jet but going up for the sake of it sounds like a bad move to me. Its done on 2strokes sometimes as it helps avoid detonation i believe and keeps the piston temp down. But thats only when you start tuning em up. Link to comment Share on other sites More sharing options...
johnsnownw Posted August 25, 2010 Author Share Posted August 25, 2010 ? The mixture screws only control a small part of the process, if you are at altitude then maybe lean her off with a smaller jet but going up for the sake of it sounds like a bad move to me. Its done on 2strokes sometimes as it helps avoid detonation i believe and keeps the piston temp down. But thats only when you start tuning em up. Well, the bike seems to run a bit on the lean side, that's why I was considering the move. The 1980+ models seem to use one size smaller than the earlier XS400's, so I didn't think it would be too much of a change. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted August 25, 2010 Moderator Share Posted August 25, 2010 Well, the bike seems to run a bit on the lean side, that's why I was considering the move. The 1980+ models seem to use one size smaller than the earlier XS400's, so I didn't think it would be too much of a change. Thinks dewps is the man to speak to for a defintite answer.. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted August 25, 2010 Moderator Share Posted August 25, 2010 i'd start by raising the mains needle 1 notch ( that's to lift the needle) if there are no grooves in the needle, put a washer under the needle base to raise it. Link to comment Share on other sites More sharing options...
johnsnownw Posted August 25, 2010 Author Share Posted August 25, 2010 i'd start by raising the mains needle 1 notch ( that's to lift the needle) if there are no grooves in the needle, put a washer under the needle base to raise it. Drewps, I was under the impression that the needle affected the midrange, does this mean raising it would make a change throughout the system? Could I not just purchase this needle (Jet Needle 5IX11) from http://www.mikesxs.net/products-37.html#products or would it also require a new needle jet. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted August 25, 2010 Moderator Share Posted August 25, 2010 Drewps, I was under the impression that the needle affected the midrange, does this mean raising it would make a change throughout the system? Could I not just purchase this needle (Jet Needle 5IX11) from http://www.mikesxs.net/products-37.html#products or would it also require a new needle jet. re-read your 1st question and it doesn't say why you need to have a richer mix. I assumed that because you were thinking of upping the mains as well as the pilot you were having an issue with the whole operating range of the bike!! I did put a smaller mains in and raised the needle and i got a stronger mid to upper power and got extra MPG! with the US bikes it may be the other way round as the emissions are stricter. Link to comment Share on other sites More sharing options...
johnsnownw Posted August 26, 2010 Author Share Posted August 26, 2010 re-read your 1st question and it doesn't say why you need to have a richer mix. I assumed that because you were thinking of upping the mains as well as the pilot you were having an issue with the whole operating range of the bike!! I did put a smaller mains in and raised the needle and i got a stronger mid to upper power and got extra MPG! with the US bikes it may be the other way round as the emissions are stricter. Ah, fair enough. Well, no, the bike has been backfiring through the carbs when coming down after acceleration, and the plugs show lean. That's why I was looking into the main and pilot. I suppose, I'm not exactly sure what to attempt first to clear up the issue. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted August 26, 2010 Moderator Share Posted August 26, 2010 Ah, fair enough. Well, no, the bike has been backfiring through the carbs when coming down after acceleration, and the plugs show lean. That's why I was looking into the main and pilot. I suppose, I'm not exactly sure what to attempt first to clear up the issue. for cheapness, try raising the needle first. I'm assuming that you checked for air leaks inc vacuumm tube on the inlet system and the ignition timing is spot on Link to comment Share on other sites More sharing options...
johnsnownw Posted August 26, 2010 Author Share Posted August 26, 2010 for cheapness, try raising the needle first. I'm assuming that you checked for air leaks inc vacuumm tube on the inlet system and the ignition timing is spot on Yeah, I checked all the normal stuff before looking at jetting. Alright, I'll give it a go with the needle. Thanks again. Link to comment Share on other sites More sharing options...
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